1. Technical Field
The present disclosure relates to a semimetal compound of Pt and method for making the same.
2. Description of Related Art
Three-dimensional semimetals are important hosts to exotic physical phenomenon such as giant diamagnetism, linear quantum magnetoresistance, and quantum spin Hall effect. Three dimensional Dirac fermions can be viewed as three dimensional version of graphene and have been realized in Dirac semimetals.
Cd3As2, Na3Bi, K3Bi, and Rb3Bi are found as three-dimensional Dirac semimetals. However, all the Cd3As2, Na3Bi, K3Bi, and Rb3Bi are type-I Dirac semimetals having a vertical cone of electron energy band as shown in FIG. 1. The type-I Dirac semimetals shows spin degenerate conical dispersions that cross at isolated momenutum points (Dirac points) in three dimensional momentum space. In a topological Dirac semimetal, the massless Dirac fermions are stabilized by crystal symmetry and could be driven into various topological phases. When breaking the inversion or time-reversal symmetry, the doubly de-generate Dirac points can be split into a pair of Weyl points with opposite chiralities, and a Dirac fermion splits into two Weyl fermions. Weyl fermions were originally proposed in high energy physics, and their condensed matter physics counterparts have been recently realized. Weyl semimetals exhibit intriguing properties, with open Fermi arcs connecting the Weyl points of opposite chiralities. Both Dirac and Weyl semimetals obey Lorentz invariance and they exhibit anomalous negative magnetoresistance.
Recently, a new type of Weyl semimetal (type-II Dirac semimetals) have been predicted. In type-II Dirac semimetals, the Weyl points arise from the topologically protected touching points between electron and hole pockets, and there are finite density of states at the Fermi level. Type-II Dirac semimetals have strongly tilted cone and thus violate the Lorantzian invariance. However, so far, the spin-degenerate counterpart of type-II Dirac semimetals have not been realized.
What is needed, therefore, is a type-II Dirac semimetals and method for making the same that overcomes the problems as discussed above.